Electric tank heater



Feb. 6, 1945. c. M. osTERHELD ELECTRIC TANK HEATER 2 Sheets-Sheet 1 Filed Feb. 3, 1943 mVENroR.

CMR/ Osma/fav BY ATTORNEY Feb- 6, 1945- c. M. osTERHELD Y 2,368,772

ELECTRIC TANK HEATER 2 sheets-sheet 2 Filed Feb. 3, 1943 Patented Feb. 6, 1945 UNITED STATES ,PATENT OFFICE ELECTRIC TANK HEATER Clark M. Osterheld, Stoughton, Wis., assgnor to McGraw Electric Company, Elgin, Ill., a corporation of Delaware Application February 3, 1943, Serial No. 474,533

6 Claims. (gCl. 21B-39) My invention relates to electric heating units and particularly to electric tank heating units.

An object of my invention is to provide a relatively simple, inexpensive and highly eflicient electric heater for domestic hot water tanks.

Another object of my invention is to provide an electric tank heater including efficient means for conducting the heat generated in the resistor to the tank.

Another object of my invention is to provide an electric tank heater having a minimum thickness of dielectric or electric-insulating material, which material is highly heat-conducting and high temperature-resisting.

Other objects of my invention will either be apparent from a description of one form of electric tank heater embodying my invention or will be pointed out in the course of such description and be set forth in the appended claims.

In the drawings,

- Figure l is a vertical sectional view of a domestic hot water tank showing the application thereto of an electric heating unit embodying my invention,

Fig. 2 is a horizontal sectional view therethrough showing the method of mounting such a heater in operative relation to the tank or of removing it therefrom,

Fig. 3 is a horizontal sectional view taken on the line 3--3 of Fig. l showing the heater mounted in proper operative position around a tank,

Fig. 4 is a fragmentary perspective view of a heating element embodying my invention,

Fig. 5 is a fragmentary perspective View of an.

inner spacing strip member comprising a part of my improved heating unit,

Fig. 6 is a fragmentary perspective view of a resistor heating element,

Fig. l is a fragmentary perspective view of an outer shroud or sheath member comprising a part of my improved heating unit,

Fig. 8 isa fragmentary perspective view of an assembly of the members shown in Figs. 5, 6 and '7,

Fig. 9 is a fragmentary horizontal sectional view showing the method of clamping an assembled heater embodying my invention, around a tank,

Fig. 10 is a fragmentary vertical sectional view taken on the line Ill-l0 of Fig. 1l, and,

Fig. ll is a front'elevational view of the parts shown in Figs. 9 and 10.

Referring first to Figs. l, 2, and 3 of the drawings I have there shown a hot water tank 2l and which is provided with a lower Coldwater'` inlet pipe 23 and an upper hot Water outlet pipe- 25. I may provide a mass 21 of'heat-insulating material around the tank and may provide a suit- 1 able outer cover 29 therefor all in a manner now well known in the art. The outer cover 29 may have a plurality of supporting legs 3l atits bottom end. The tank 2l may be spaced from the lower part of outer casing 29 by a plurality of bl-ocks 33 which may be of,wood or of any other` suitable non-heat-conducting material lused in the art.

I provide a tunnel member 35 aroundthe tank 2| and any suitable or desired material may be used to build up the top, the bottom and they At one part; of the periphery of the tunnel 35 I provide-an; opening 31 which may be normally covered by, ai; closure member 39 all as now Well known in the art. I have not shown any means for holding the tunnel member in the desired position since outer wall of such tunnel member.

means effective for this purpose are well known in theart and form no -part of my present invention. Referring now to Figs. 5 to.8 inclusive I have there shown an inner or spacer strip 4I which is 1 preferably, although not necessarily, made ofv relatively thin aluminum, the thickness of whichmaybe on the order of .015 or slightly larger'.l The entire outer surface of this' spacer strip lll may have provided thereon an integral anodic' coating as is shown by the stippling in Figs. 5, 6

and 8 of the drawings and by 'such coatings Ifv refer not to the relatively very'thin norm-al or usual coating occurring on the surface of aluminum members when exposed to the air. Thel integral anodic coating above referred to isthat.'

lobtainable by electrolytic methods now well known in the artor by immersion of aluminum articles in a suitable solution whereby a coating having a thickness on the order of .0015'T or slightly more is provided on the surface.

without cracking, flaking .or breaking thereofwhen the material to which it is coherent is bent to some other shape.

,This` coating is of a dielectric nature or as may be.

Such a coating is not ad-. herent but is an integral part of the aluminumsurface. I desire it to be further understood that- While I prefer to use aluminum for the inner or'f spacing strip I do notfdesire to be limited thereto' which is of the usual domestic kind used in homes since it has been ldiscovered that Qtllel! metals" ingr the above mentioned characteristics.

I have illustrated in Fig, 6 a .flat strip resistor conductor 43 which is preferably also made of aluminum and which may have provided thereon an anodic coating having the above described characteristics which will permit of winding the resistance conductor 43 in close operative engagement around Ia strip 45 with the adjacent turns thereof in close operative engagement. This permits of obtaining a greater heating capacity for any given length of coiled resistance conductor 43 and such resistor element therefore clearly `distinguishes from the kind which it is now necessary to use wherein an appreciable space vmust be left unoccupied between adjacent turns to prevent breakdown therebetween all as is now well known in the art. It is to be noted that it is `not necessary that the conductor 43 be provided with an anodic coating since it is only necessary under such 'conditionsfthat the adjacent turns be out of operativeengagement with each other to prevent breakdown therebetween. 'While vI have `above stated thatI-prefer to use aluminum conductors Ilm not liimited thereto since resistance conducton now well known in the art such as Nichrcme maybe used'andprovided or not, as above stated, with an anodic coating.

The resistor supporting strip 45 may be made, and I prefer to make it,voirelatively thin aluminumon the order of 015", thick which strip is preferably provided with an anodic coating having the 4above described characteristics. It is therefore'evident that if the conductor 43 has an anudic coating there will 'be two thicknesses thm'eofllbetween the conductor and the metallic supporting istrip `45 around which the `conductor is wound asiabove described. However if the conductor is not provided with an anodic coating there will still -be one "thickness of such electricinsulating coating :between the conductor and the rapport 45.

I wish 'further to `po'in't vout here that it is not necessary that the strip 45 be of metal but it may be made 'df any other 'suitable material having electric-insulating characteristics such `as mica or micanite `or perhaps `other materials having electric-insulating characteristics which `are at the Asame time sufllciently flexible `to permit of ming bent around a hot water tank or around any other suitable appliance or apparatus which is to have'the heater voperatively associated therewith and have sumcient strength to withstand the .tension .to which it `will be subjected lwhen clamped tightly around a tank.

.The strip 45 has end portions 4'! bent at right angles thereto, each .end `portion haw'ng mechanically operatively secured thereto an L-shaped lug '43, for strengthening purposes. The length ofthe strip 45 is made such that the end portions 41 will be spaced apart a small distance as is snownby reference to Figs-3 and 9 of the drawings for purposes to be hereinafter referred to in detail It is obviousthat, 'generally speaking, there are two 'directions in which the heat generated in `a resistor 'of this kind may flow relatively to the tank Tl, the first oi' 'these `'directions being that from the conductor to the tank and the second being from the conductor away from the tank. Where *the strip 45 `is of appreciable width say on 'fthe 'orderof one-or more inches, as may be found desirable or suitable, the heat generated in that part of the resistance conductor operattvaly engaging the inner 'side of the strip `45 may have provided thereon anodic coatings havwill flow in the rst direction while the heat generated in that part of the conductor adjacent to the outer side of the strip 45 will ilow outwardly and unless effective means are provided for receiving this heat and causing it to flow toward and then into the tank 2| this heat will belost.

Referring now to Fig. 'l of the drawings I have there illustrated a shroud or outer sheath member 5| which member is of flattened channelshape in lateral section. While I prefer to make the shroud member 5| of relatively thin aluminum I do not desire to be limited thereto, but prefer aluminum because of its high heat conductivity. The side edge portions 53 of member i 5| are made relatively wide and the two side portions are not co-planar but the planes thereof extend at an angle slightly less than but approaching relatively to each other, so that when clamped around a tank the entire lateral faces or surfaces of the side edge portions thereof will engage the outer tank surface. I provide a clamping lug `55 at each end of the sheath or cover member 5l for a purpose to be hereinafter referred to.

Shroud 5| is provided with a plurality of spaced openings 51 therein adapted to receive securing lugs 53 which are either integral with or secured to the spacing strip 4| at the side edges thereof. I have shown, in Fig. 8, the members 4|, 43, 45 and 5| when assembled in proper operative positions relative to each other and before they are mounted around a tank. End portions of the conductor 43 may extend outwardly through openings 6| in the sheath and if the resistance conductor 43 is provided with an anodic coating itwillmake `no appreciable difference if there is operative contact `between the conductor 43 and the walls of thefopening 6I inthe shroud 5I.

Referring now to Fig. 2 of the drawings I lhave there shown a method of mounting the heating element comprising members 4|, 43, 45 and 51 in the tunnel 35 and the heating nunit is shown as having already been partially moved into the tunnel and around the tank 2|. When the heating unit has been moved into proper operative position in the tunnel 35 with the lower side edge portions 53 resting on the lower wall of the tunnel, the lugs '49 `and 55 'being symmetrically `located with regard to the side walls, a clamping means comprising a screw threaded rod 63 may then be extended `through these lugs through openings therein. Nut 65 may iirst be provided on the rod 63 to engage the two lugs 49 and proper turning movement of the nuts 65 on the rods 63 toward each other will serve to clamp tightly the heating unit against the outer surface of the tank. The clamping tension applied to the lugs 49 or end of strip 45 will cause tight operative engagement of the `heating element comprising particularly the supporting strip 45 and the resistor conductor 43 `wound thereon against the outer surface of the spacing strip 4| and will also cause good heat conducting engagement between the inner side or surface of the strip y4| and the cuter `surface lof the tank 2 l. A pair vof nuts 51 may then be tightened on the rod 63 into clamping and tensioning engagement with the lugs 55 whereby the shroud 5| is moved into good heat-conducting engagement with the conductor 43 and the outer surface of the tank. It is obvious that ther'centralportion of strip 5| will be caused to closely engage the conductor 43 and those parts thereof on the outside of the strip 45 while the side edge portions 53 heating element propel'.

will be caused to closely engage the outer surface of the tank immediately adjacent to the The entire surface of each of the side edges will be moved into engagement with the outside surface of the tank as is shown more particularly in Fig. 10 of the drawings so that the heat flow path from the conductor 43 into the shroud 5l and from the shroud El to the outside surface of the tank will have a` relatively lou7 thermal reluctance.

Referring now particularly to Fig. 4 of the drawings I have there illustrated another form of heating element comprising a supporting strip 69 which is of the same general character as the strip 45 hereinbefore described and which has wound thereon a resistance conductor 1| which may be of Wire form. IThe resistance conductor 'H `may be provided with an anodic coating of the hereinbefore described kind so that the adjacent turns thereof may be Wound closely on the strip E9 and be in operative engagement with each other as is shown in Fig. e. The strip 69 is provided with a lug 'I3 of substantially L-shape and is bent over an end portion 'I5 at each end thereof so that the strip E9 with the conductor 'Il mounted or wound thereon may be clamped around a tank 2i as has already been hereinbefore described in connection with the strip 45 and the conductor 53.

Reference to Figs. 8, l0 and l1 will show one method of securing members 4|, 43, 45 and 5l in proper operative positions relatively to each other. It will be noticed that the outer end portions of lugs Eli may be bent over against the midportion of shroud 5l but it is not necessary that f any appreciable pressure be provided by this means since the shroud 5I and its tensioning clamping means hereinbefore described will hold the parts in close operative engagement around a tank as has already been hereinbefore described.

Various modii'lcations may be made in the device embodying my invention Without departing from the spirit and scope thereof and vall such modications clearly coming Within the scope of the appended claims are to be considered as being covered thereby.

I claim as my invention:

l. An electric heating unit adapted to be mounted around a domestic -hot water tank, said unit comprising a heating element consisting of a strip of material having electric-insulating characteristics and a resistor conductor wound therearound, a metallic sheath, of substantially channel-shape in lateral section covering said heating unit, said resistor conductor and at least the inner surface of the sheath having thereon an inorganic, integral, heat-conducting, high temperature-resisting and electric-insulating coating an means to draw the ends of the strip cf material toward each other to hold the parts of the turns of the resistance conductor adjacent to the inner surface of the strip of material in good operative heat conducting engagement with the outer surface of a tank and means to draw the ends of said metallic sheath toward each other to hold the mid-portion of the sheath in good heat-conducting engagement with the parts of the turns of the resistance conductor adjacent to the outer surface of the strip of material and to hold the edge portions of the sheath in good heat conducting engagement with the outer surface of the tank.

2. An electric heating unit adapted to be mounted around a hot water tank, said unit comprising an inner metallicvspacer strip'extending around a tank, a resistor-supporting strip having electric-insulating characteristics, a metallic resistor conductor Wound on said resistorsupporting strip, a metallic sheath, of substantially channel-shape in lateral section, extending circumferentially of a tank outside of said spacer and said resistor-supporting strip, the outer surface of said spacer strip, and the inner surface of said sheath having thereon an integral, inorganic, heat-conducting, high temperatureresisting and electric-insulating coating and adjustable clamping means mechanically engaging the end portions of said sheath to draw the ends thereof toward each other and cause it to clamp the resistor-supporting strip and the resistor thereon into good heat-conducting operative engagement with the tank and to press the side portions of the sheath into good heat-conducting engagement with a tank.

3. An electric heating unit adapted to be secured around a hot water tank, said Unit comprising an inner metallic spacer strip lto extend around a tank, a metallic resistor-supporting strip adapted to extend around a tank outside of said spacer strip, a resistor conductor Wound around said resistor-supporting strip, a metallic sheath, of substantially flat channel shape in cross section adapted to extend around a tank outside of said resistor-supporting and said spacer strip, the outer surface of the spacer strip, the entire surface of the resistor-supporting strip and the inner surface of the sheath having thereon an inorganic, integral, heat-conducting, high temperature-resisting and electric-insulating coating and adjustable mechanical -means engaging said resistor-supporting strip and said sheath to draw the end portions thereof toward each other to hold them tightly on the tank.

4. An electric heating'unit adapted to be secured around a hot Water tank, said heating unit comprising a metallic resistor-supporting strip adapted to extend around a tank, a resistance conductor Wound on and around said strip, said r conductor having thereon an inorganic, integral,

heat-conducting, high temperature-resisting and electric-insulating coating, a sheath, of substantially channel-shape in cross-section, adapted to extend around a tank outside of said strip and conductor in operative engagement with the resistor conductor and the outer surface of a tank and adjustable mechanical means engaging the end portions of the strip and of the sheath to draw the end portions toward each other and thereby cause good heat-conducting engagement between the resistance conductor and the tank, between the resistance conductor and the sheath and between the sheath and the tank.

v5. An electric heating unit adapted to be secured around a hot Water tank, said heating unit including a metallic spacing strip to extend around a tank, a metallic resistor-supporting strip adapted to extend around a tank outside of said spacing strip, a metallic resistor conductor wound around said resistor-supporting strip, a metallic sheath, of substantially flat channel-shape in cross-section adapted to extend around a tank outside of said tWo strips and resistor conductor, at least the outer surface of said spacing strip, the entire surface of said resistor-supporting strip and of the resistance conductor and at least the inner surface of the sheath having thereon an inorganic, integral, heat-conducting, high temperature resisting and electric-insulating coating and a single adjustable clamping means operatively connected to the end portions of the resistorsupporting strip and of the sheath to draw the opposing end portions toward each other to cause the sheath to be pressed into good heat-conducting engagement with those portions of the resistance conductor located against the outer surface of the resistor-supporting strip and into good heat conducting engagement with the tank, to cause those portions of the resistance-conductor located against the inner surface of the resistorsupporting strip into zood heat conducting engagement with the spacing strip and to press the spacing strip into good heat-conducting engagement with the outer surface of a tank.

6. An electric tank heating unit adapted to be mounted around a hot water tank, said heating unit comprising an inner metallic spacer strip to extend around a tank, a metallic resistor-supporting strip adapted to extend around a tank outside of said spacer strip, a resistor conductor Wound on and around said resistor-supporting strip, a metallic sheath of substantially nat channel-shape in lateral section adapted to extend around a tank outside of said resistor-supporting and said spacer strips, the surface of said spacer strip, the surface of said resistor-conductor and the surface of said sheath having thereon an inorganic, integral, heat-conducting, high temperature-resisting and electric-insulating coating and adjustable mechanical means engaging the end portions of said resistor-supporting strip and said sheath to draw the said end portions toward each other to clamp said resistorsupporting strip and said sheath tightly around a tank.

CLARK M. OSTERHELD. 

